7 Способов решения Палиндромных программ на Python
Строки и числа, которые одинаковы, даже если они перевернуты, являются палиндромами. Мы можем проверить, является ли строка или число палиндромом в Python.
- Автор записи
Один из самых простых и часто задаваемых вопросов на интервью – проверить, является ли строка палиндромом или нет, используя Python.
Палиндром – это строка или число, которое, если повернуть вспять, равно исходному значению. Например, если мы перевернем строку MALAYALAM, мы получим обратно исходную строку. Кроме того, если мы перевернем число 12321, мы получим 12321 обратно. Они известны как палиндромы.
В этой статье мы узнаем, как проверить, является ли строка или число палиндромом или нет, разными способами. В дополнение к этому мы решим некоторые вопросы болельщиков, которые обычно задаются на соревнованиях и интервью.
В этой статье мы узнаем, как проверить, является ли строка или число палиндромом, различными способами. В дополнение к этому мы решим несколько интересных вопросов, которые обычно задаются в конкурсах и интервью.
Проверка того, является ли строка палиндромом в Python
- Проверьте Палиндром с помощью нарезки (slicing) в Python
- Проверьте Палиндром с помощью функции reversed() В Python
- Проверьте Палиндром с помощью цикла while в Python
- Проверка того, является ли число палиндромом в Python с помощью цикла
- Проверка того, является ли фраза палиндромом в Python
- Как найти самую длинную палиндромную подстроку в строке
1. Проверьте Palindrome с помощью нарезки в Python
Мы можем использовать концепцию нарезки, чтобы перевернуть строку, а затем мы можем проверить, равна ли перевернутая строка исходной строке или нет.
Вышеприведенный метод прост в использовании, а также хорош, и вы можете использовать его на соревнованиях, но люди обычно не предпочитают использовать его в интервью. Этот метод настолько прост, и люди предпочитают кодировать с нуля, чтобы сделать такую программу, чтобы показать свои навыки. Мы также рассмотрим этот подход в следующем разделе.
How to do check for a palindrome in Python?
Hi I’m working on a python function isPalindrome(x) for integers of three digits that returns True if the hundreds digit equals the ones digit and false otherwise. I know that I have to use strings here and this is what I have:
the str(0) is the units place and str(2) is the hundreds place. All I’m getting is False? Thanks!
11 Answers 11
Array access is done with [] , not () . Also if you are looking for hundreds and units, remember that arrays are 0 indexed, here is a shortened version of the code.
You might want to take in the number as a parameter and then convert it to a string:
Note that you can simply just check if string is equal to it’s reverse which works for any number of digits:
str(1) will create a string of the integer value 1. Which won’t equal the string value of the integer value 3 — so it’s always False.
You should return True and False , rather than strings of «True» and «False».
This is what you’re aiming for taking into account the above. (which works with any length)
Your problem is that str(1) == ‘1’ and str(3) == ‘3’ . You’re also returning string values reading ‘True’ and ‘False’ instead of using the actual True and False values.
Let me propose a much simpler function for you:
s[::-1] creates a reverse of the string; e.g. ‘foo'[::-1] == ‘oof’ . This works because of extended slice notation.
Not sure why people are sticking to the string idea when division and modulo will do:
if the number is no larger than 999 (3 digits as the OP stated) then it simplifies to
str() casts a value into a str . You want to access each character. You might want to benchmark a few different techniques.
So, it looks like the mod technique works:
str(1) just gives you the string representation of the number 1 :
What you want is the first index of the string representation of x .
you compare number 1 and 3, but you needt to compare index of input variable.
It looks like you still need to study Python syntax
Here is a way to achieve what you need :
str(x) delivers the string value of whatever you pass to it, so in your case the string «1» or the string «3» . But what you actually want is to access the 1st and 3rd digit of the given number. So, first you want to convert that number to string (e.g. with str(num)), and then you have to consider that indices in strings begin with 0, not with 1. So working code culd e.g. look like this:
A smaller solution for this would be:
This will work for words and integer values.
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Palindrome in Python
Today we are going to learn about the palindrome series and how to implement and identify a palindrome in Python. So let’s dive right into it!
What is a Palindrome?
A number is defined as a Palindrome number if it reads the exact same from both forward and backward. And the crazy thing is that it is not only valid to numbers. Even if a string reads the same forwards and backward, then it is a Palindrome as well!
Let us look at some examples to understand it better.
What is a Palindrome series?
1. Palindrome Numbers
Let us consider two numbers: 123321 and 1234561.
The first number 123321, when read forward and backward is the same number. Hence it is a palindrome number.
On the other hand, 1234561, when reading backward is 1654321 which is definitely not the same as the original number. Hence, it is not a Palindrome Number.
2. Palindrome Strings
The logic that was explained for the Palindrome Numbers is also applicable to the strings. Let’s consider two basic strings: aba and abc.
String aba reads the same no matter how it is read (backward or forward). But on the other hand string abc when reading backward results in cba which is not same as the original string.
Hence aba is a Palindrome while abc isn’t.
How to verify for Palindrome?
1. Palindrome Numbers
To check if a number is a Palindrome number or not, we first take the input of the number and create a copy of the number taken as an input.
We then create a new variable to store the reversed number and initialize it with 0.
Traverse through the number using mod 10 and division by 10 operations and in each loop make sure to add the digit in the reversed number variable*10.
2. Palindrome Strings
To check for a string, we take a string as input and calculate its length. We also initialize an empty string to store the reverse of the string.
We create a decrementing loop starting from the last index and going to the first and each time concatenate the current reversed string with the new letter obtained.
Pseudo-code to implement Palindrome in Python
1. Palindrome Numbers
2. Palindrome Strings
Code to implement Palindrome Checking in Python
Now that you know what Palindromes are and how to deal with them in the case of strings and numbers, let me show you the code for both.
1. Palindrome Implementation: Numbers
Let’s check for palindrome numbers using Python.
2. Palindrome Implementation: Strings
Let’s now check for Palindrome strings in Python
Palindrome Numbers
Palindrome Strings
Conclusion
Congratulations! Today in this tutorial you learned about Palindromes and how to implement them as well! Hope you learned something! Thank you for reading!
7 Ways to Solve Palindrome Python Programs
One of the most basic and commonly asked interview questions is to check whether a string is a palindrome or not using python. A palindrome is a string or a number that, if we reverse, equals the original value. For example- if we reverse the string MALAYALAM, we will get back the original string. Also, if we reverse the number 12321, we will get 12321 back. These are known as palindromes.
In this article, we will learn how to check whether a string or a number is a palindrome or not in many different ways. In addition to it, we will solve some fun questions which are commonly asked in competitions and interviews.
Checking Whether a String is a Palindrome in Python
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Check Palindrome Using Slicing in Python Check Palindrome Using reversed() Function In Python Check Palindrome Using Using While Loop In Python Checking Whether a Number is a Palindrome in Python Using Loop Checking Whether a Phrase is a Palindrome in Python To find the Palindromic longest substring in a string
1. Check Palindrome Using Slicing in Python
We can use the concept of slicing to reverse the string, and then we can check whether the reverses string is equal to the original string or not.
The above method is straightforward to use and also a good method, and you can use it in competitions, but people generally don’t prefer to use it in interviews. This method is so simple, and people prefer to code from scratch to make this kind of program to show their skills. We will study that approach too in the following section.
2. Check Palindrome Using Loop In Python
3. Check Palindrome Using reversed() Function In Python
4. Check Palindrome Using Using While Loop In Python
5. Checking Whether a Number is a Palindrome in Python Using Loop
We are going to use the following concept-
Number=12321
The remainder of this number, when divided by 10, is:
Number%10=12321%10=1
Reverse_Number=Remainder=1
Then, we will divide the number by 10.
Number=Number/10=12321//10=1232
Remainder=1232%10=2
Reverse_Number=Remainder=12
Number= 1232/10=123
Remainder=123%10=3
Reverse_Number=Remainder=123
Number= 123/10=12
Remainder=12%10=2
Reverse_Number=Remainder=1232
Number= 12/10=1
Remainder=1%10=1
Reverse_Number=Remainder=12321
We can also first convert the number into a string and then apply any of the methods above to check if the number is palindrome or not.
6. Checking Whether a Phrase is a Palindrome in Python
Checking if a phrase is a palindrome or not is different from checking if a word is a palindrome or not. So, we cannot apply any of the above methods for a phrase.
For example- The phrase ‘Too hot to hoot’ is a palindrome if you ignore the upper case – lower case and spaces in the characters.
There are some other types of palindromes, like- ‘Is it crazy how saying sentences backward creates backward sentences saying how crazy it is.’ It is different from other palindromes we have discussed until now because here, if we reverse the characters, it is not a palindrome. But if we reverse it word by word, it is a palindrome.
7. To find the Palindromic longest substring in a string
A very common and interesting question on palindromes is to find the longest substring, which is a palindrome from a string that may or may not be a palindrome. I suggest you try it yourself once and then look at the solution below.
There are many ways to solve this problem. We will go for the easiest one which all of us will be able to understand easily.
The time complexity for the above program is O(n^2) as we have a for loop inside a for a loop.
Must Read
Conclusion
We have studied what a palindrome is, how to check whether a string or a number is a palindrome. We have also covered some common interview questions like checking for a phrase if it is a palindrome and finding the longest substring, which is a palindrome in python. I hope you will try each problem, and please comment down if you face any issues in it.